1. Field of the Invention
The present invention relates to a hydraulic system for a detachable implement having multiple hydraulic motors and in particular to a hydraulic system for a harvester header, such as a draper platform.
2. Description of Related Art
Draper platforms for harvesting machines, such as a combine, have a flat, wide belt, referred to as a draper or draper belt, to convey crop material. The arrangement and number of draper belts vary among platforms. One style of draper platform has two side belts that convey crop material laterally, to the center of the platform, where a center feed draper belt moves the crop material longitudinally into a combine feederhouse. Each of the draper belts is driven by a hydraulic drive motor.
In addition to the draper belts, a draper platform uses another hydraulic motor to rotate a reel above a cutterbar to hold crop material against the cutterbar and to move the cut crop material onto the draper belts. Hydraulic lift cylinders are used to raise and lower the reel as well as to position the reel fore and aft relative to the cutterbar.
A conventional combine includes a hydraulic system with connections for driving the platform reel and connections for operating the reel lift cylinders and the reel fore and aft adjustment cylinders. In addition to the hydraulic connections to the platform, the combine includes a power take off (PTO) for a mechanical power connection. The PTO is typically used to mechanically drive the platform cutterbar and crop conveying augers if the platform is so equipped.
Combines typically do not have additional hydraulic power connections for operating the draper belt drive motors. Therefore other provisions must be made for providing hydraulic power for this purpose. One option is to provide a complete hydraulic system on the platform including a gear pump that is driven by the combine PTO. This approach requires that the platform hydraulic system be equipped with a reservoir, filter and cooling package. This adds significant cost, weight and complexity to the draper platform. In addition, the PTO shaft speed is typically lower than required for efficient operation of a gear pump.
A second option is to provide additional pump capacity on the combine, thereby utilizing existing combine hydraulics to power the draper belt drive motors. A major disadvantage with this approach is the need for significant combine modifications in retrofit applications, as well as the need for another set of hydraulic hoses and couplers between a combine and the platform.
Accordingly, it is an object of the present invention to provide a hydraulic system for a detachable implement, such as a draper platform, that does not require modification to the existing combine hydraulic system and which does not require the added cost, weight and complexity of a complete hydraulic system onboard the platform.
The hydraulic system of the present invention utilizes a platform-mounted pump, supplied with return oil from the reel drive motor. The system utilizes the existing combine hydraulic connection for the reel drive. Oil from the combine powers the reel drive motor and then flows into a manifold block (mixing chamber) before entering the inlet of the draper belt drive pump. This pump is sized to provide sufficient oil flow to power the draper belt drive motors, arranged in series. Return oil from the belt drive motors is routed back to the manifold block where it can mix with incoming oil from the reel drive pump before returning to the combine reservoir or being recirculated to the belt drive motors.
At the upper end of the reel speed range, oil flow from the reel drive motor is sufficient to supply the needs of the belt drive pump, in which case all returning oil from the belt drive motors is immediately routed back to the combine. At the lower end of the reel speed range, oil from the reel drive motor may not be adequate to supply the entire demand of the belt drive pump, so a portion of the return oil from the belt drive motors will recirculate within the belt drive system, instead of immediately returning to the combine. The ports in the manifold block are configured such that the belt drive pump receives its priority oil from the reel drive motor return, and only draws its own return oil when necessary. The utilization of the oil from the reel drive motor as the priority oil together with the long oil flow path from the pump, through the motors and back to the manifold prevents excessive heat buildup in the belt drive hydraulic oil. The hydraulic system thus uses the belt drive pump to provide the desired oil flow from the reel drive circuit to drive the draper belt motors. No additional hydraulic connection to the combine is needed.
A unique aspect of the hydraulic system is the use of an Eaton T-Series Geroler motor as a pump. This motor was selected as the pump due to its low speed, high torque characteristics. In addition, this motor operates more efficiently at the low shaft speed available on the platform compared to gear pumps. Combine back pressure in the reel motor return will provide positive pump inlet pressure. The T-Series motor is not able to draw oil but combine back pressure provides this service. The T-Series motor was selected since the shaft seal can withstand back pressures up to 1500 psi. The high combine back pressure is not suitable for most gear pumps.
While the present invention has been developed for use with a draper platform for a combine, the hydraulic system of the present invention can be utilized in other applications where an implement is attached to a prime mover and utilizes two or more hydraulic drive motors, with one motor being driven by a connection to a hydraulic system on the prime mover. Other uses may include agricultural tractors and implements as well as construction equipment with detachable implements.